Are all credit score websites accurate in determining your score?

I just paid $5.95 on Transunion (from www.annualcreditreport.com) to get my credit score after being able to view my credit report for free and I got an 819 out of 925 and was rated as only ';good';. Other credit score postings say 819 would count as God-like status. I just wanna make sure that's a reliable conclusion. And what does this mean when I (first time homebuyer, so not super rich) plan on applying for a loan.